The present invention relates to displays, and more particularly to processes for creating spacer attachment sites for a field emission display (FED).
Referring to FIG. 1, in a typical FED (a type of flat panel display), a backplate (cathode) 21 has a substrate 10, such as glass, on which conductive layers 12, such as doped polycrystalline silicon or aluminum, are formed. Conical emitters 13 are formed on conductive layers 12. A dielectric layer 14 surrounds emitters 13, and a conductive extraction grid 15 is formed over dielectric layer 14. When a voltage differential from a power source 20 is applied between conductive layers 12 and grid 15, electrons 17 bombard pixels 22 of a phosphor coated faceplate (anode) 24. Faceplate 24 has a transparent dielectric layer 16, preferably glass, a transparent conductive layer 26, preferably indium tin oxide (ITO), a black matrix grille (not shown) formed over conductive layer 26 to define regions, and phosphor coating over the regions defined by the grille.
Backplate 21 and faceplate 24 are spaced very close together in a vacuum sealed package. In operation, there is a potential difference on the order of 1000 volts between conductive layers 12 and 26. Electrical breakdown must be prevented in the packaged FED, while the spacing between the plates must be maintained at a desired thinness for high image resolution.
A small area display, such as one inch (2.5 cm) diagonal, may not require additional supports or spacers between faceplate 24 and backplate 21 because glass substrate 16 in faceplate 24 can support the atmospheric load. For a larger display area, several tons of atmospheric force are exerted on the faceplate, thus making spacers important if the faceplate is to be thin and lightweight.
The present invention includes methods of making spacers in displays and particularly in field emission displays (FEDs). One method includes steps of mixing frit and photoresist together to form a mixture, applying the mixture to a surface of a portion of a faceplate or backplate, removing portions of the mixture to form adhesion sites at desired locations, and attaching spacers at the adhesion sites. In preferred embodiments, the mixture has about 2% frit and 98% photoresist and is provided on a grille and a transparent conductive layer of a faceplate, and is then removed except over portions of the grille.
With the method of the present invention, precise adhesion sites can be conveniently formed. Other features and advantages will become apparent from the following detailed description, drawings, and claims.